The plan for EVAR Sizing

Before an endovascular aneurysm repair, someone measures the patient's CT scan: how wide the aorta is just below the kidneys, how long that healthy neck runs before the aneurysm starts, how wide the aneurysm gets, and how wide each iliac artery is. Those numbers decide which stent graft fits. EVAR Sizing is a place to practise taking them and find out how close you were.

What I'm trying to do

Practice with an answer key. Trainees measure synthetic and real scans and get every number checked, then pick a graft from the Medtronic, Gore and Cook sizing tables.
A study of how the skill grows. Anyone who joins has each attempt kept under a random id, so students, residents, fellows and staff surgeons can be compared over training. The study needs ethics approval before its data is used.
More real scans. Real CT from openly licensed collections, each measured once by a resident so it has answers to check against.

How a case works

Pick a case: a synthetic phantom, or a real scan.
Measure: scroll the slices and put calipers on the neck, the sac and both iliacs.
Size the graft: choose a main body and limbs from a maker's sizing table.
See how close you were: each number against its answer and the tolerance it's graded at.

The guide goes through each measurement with pictures.

What it costs

Everything here is in Canadian dollars. Most of these services bill in US dollars, so each US price is converted at the Bank of Canada's rate for October 23, 2026: US$1 = $1.3993. The prices are each company's list price on that day.

A year of it costs about $609 at its quietest and $890 at its busiest: storage, servers, delivery and the domain, my 10% upkeep fee for looking after it, and my $500 base fee, which is charged once. Storage and delivery are estimates, because I don't know the actual sizes of the scans yet. A resident's time to set each new scan's answers is left out unless it's switched on below. Paid at $50 an hour and 15 minutes a scan, it would be $12.50 a scan: $125 for 10 scans and $12,500 for 1,000.

Count a resident's time to set each scan's answers

Off: every total below is what running the site costs. Turn it on if the resident is paid for each scan.

Estimate it

The sliders start on the middle case: 100 scans, 50 people a day doing 30 each, for 1 year. Their tops are the biggest case I've planned for. With the resident's time counted, two more start at $50 an hour and 15 minutes a scan.

Scans in the library

People a day

Scans each a day

How long

$608.92for 1 year

What the total is made of
Line	Cost	How it's worked out
API and database (Railway)	$84.00	Hobby, US$5 a month with that much usage included.
Scan delivery (CloudFront)	$0.00	Inside CloudFront's free terabyte a month. The 8.99 MB a scan is an estimate.
Scan storage (S3)	$0.38	899 MB at US$0.025 a GB a month. The 8.99 MB a scan is an estimate.
Domain (.com)	$14.64	A regular .com, paid a year at a time. Other names and endings cost more or less.
Website (Vercel Hobby)	$0.00	Free while the site is non-commercial.
Sign-in (Auth0)	$0.00	Free up to 25,000 people a month.
My base fee	$500.00	Once, for my services, and not part of the 10% upkeep fee.
My upkeep fee (10%)	$9.90	A tenth of running the site, never of the resident's time: upkeep, new scans and admin access for residents.

45,000 scan opens a month, 404.55 GB of data.
94,500 of Vercel Hobby's 1,000,000 function calls a month.
1.08 GB of study records by the end.

The range

The range, from the smallest case to the biggest
How long	Smallest10 scans, 10 people a day doing 10 each	Middle100 scans, 50 people a day doing 30 each	Biggest1,000 scans, 100 people a day doing 100 each
3 months	$539.22	$539.30	$609.51
6 months	$562.33	$562.51	$702.92
1 year	$608.55	$608.92	$889.72
2 years	$717.10	$717.83	$1,283.37

Every total includes my $500 base fee, charged once, and my 10% upkeep fee on running the site. Counting a resident's time, at $50 an hour and 15 minutes a scan, would add $125 to the smallest case and $12,500 to the biggest.

Where the money goes

Storing and delivering the scans

The size of the scans is an estimate. I don't know the actual sizes of the scans going into the library yet, so the space, storage and delivery figures here assume each one is 8.99 MB, the size of the one real scan I've prepared so far: cropped to the aorta, one byte a voxel, and compressed. They're what scans like that one would cost, rather than a quote.

Amazon S3 in Canada charges US$0.025 a GB each month to keep them. With the switch on, the table also shows a resident's time to measure each one.

The library: storage by number of scans
Scans	Space	Storage for a year
10	90 MB	$0.04
50	450 MB	$0.19
100	899 MB	$0.38
500	4.5 GB	$1.89
1,000	8.99 GB	$3.77

Each time someone opens a real scan, their browser downloads it. CloudFront's first terabyte a month is free, about 111,234 opens. Past that it's US$0.085 a GB, until the flat-rate Pro plan, US$15 a month for 50 TB, is the cheaper way. The phantoms are drawn in the browser, so they cost nothing to deliver.

Scan delivery a month, by people a day and scans each a day
People a day	10 scans each	30 scans each	50 scans each	100 scans each
10 people a day	$0.0026.97 GB	$0.0080.91 GB	$0.00134.85 GB	$0.00269.7 GB
50 people a day	$0.00134.85 GB	$0.00404.55 GB	$0.00674.25 GB	$20.991,348.5 GB
100 people a day	$0.00269.7 GB	$0.00809.1 GB	$20.991,348.5 GB	$20.992,697 GB

Running it

The services it runs on
Service	What it does	Plan and list price	In Canadian dollars
Vercel	Serves the pages. The phantoms are drawn in the browser.	Hobby, free for a non-commercial site, with 100 GB of data, 1,000,000 function calls and 4 CPU hours a month. Pro is US$20 a month.	$0.00Pro: $27.99 a month
Railway	Runs the API and the study's database.	Hobby, US$5 a month, which includes that much usage. Memory is US$10 a GB, CPU US$20 a core and disk US$0.15 a GB, each a month.	$7.00 a month
Auth0	Signs in anyone who joins the study.	Free, up to 25,000 people a month, with one custom address for the sign-in page.	$0.00
Amazon S3	Keeps the real scans.	US$0.025 a GB a month, in Canada (Central).	$0.31 a monthfor 1,000 scans
Amazon CloudFront	Delivers the scans to browsers.	The first terabyte a month free, then US$0.085 a GB, or US$15 a month flat for 50 TB.	$0.00up to $20.99 a month

What my fees cover

My base fee is $500, charged once for my services, and it isn't part of my 10% upkeep fee. The upkeep fee is 10% of running the site, on every total here, and never on the resident's time. It covers:

Upkeep. Updates, security fixes, and keeping the site, the API and the database running, including when a host has an outage.
New scans. Moving each new scan to where it needs to be: preparing it into the practice's format, putting it in storage, and adding it to the list, ready for a resident to measure.
Admin access. Adding a resident's email to the admin list, so they can sign in and set each scan's answers.
Small fixes and changes along the way. Bigger new features are priced on their own.

Adding more scans

My part, preparing each scan and moving it into storage and onto the list, is in my fee. Each scan then needs a resident to measure it on the admin page and enter its five answers, so there's something to grade against. If that's paid, at 15 minutes a scan and $50 an hour it's $12.50 a scan, which the switch above adds to the totals.

What one more scan takes
Step	Who	Time	Cost
Prepare the scan with the script	Me	A few minutes	In my fee
Move it into storage and onto the list	Me	A few minutes	under $0.01
Measure it and enter its five answers	A resident	About 15 minutes	$12.50 if paid
Keep it stored	S3	Ongoing	under $0.01 a year

For a sense of the time: in a Leiden study, six observers took 20 sizing measurements on each of 20 scans, and it took 9.5 to 11 minutes a scan whichever planning software they used. Five measurements here, with time to check them, is about 15. A second resident measuring each scan on their own, so the two answers can be compared, doubles the resident's line.

A domain of its own

Cloudflare sells domains at what the registry charges, with WHOIS privacy included, and renews them at the same price. A .ca needs a Canadian presence. DNS comes with the domain and Vercel issues the HTTPS certificate, so neither costs anything.

A domain, by ending
Ending	First year	Each year after
.com	$14.64	$14.64
.ca	$12.86	$12.86
.org	$11.89	$15.67

The domain's cost depends on the name chosen. The totals use a regular .com at Cloudflare's at-cost price. Another ending costs more or less, a premium or already-owned name can cost hundreds or thousands of dollars to buy, and registries can raise renewal prices, so the domain line is what an ordinary name costs rather than a quote.

Everything else

Everything else
Item	Cost	Notes
A contact address at the domain	$0.00	Cloudflare Email Routing forwards it to my inbox. It only receives.
A mailbox that can also send	$9.20 a month	Google Workspace Business Starter, one person, with a one-year commitment. Optional, and not in the totals.
Ethics review for the study	$0.00 expected	Unfunded studies usually aren't charged. Industry-sponsored ones are: the University of Waterloo charges $3,500 for an initial review. It's needed before the study's data is used.
Scan licences	$0.00	Open collections under CC BY 4.0, credited on the page.
The intro video	$0.00	Recorded from the practice itself.
My time	In my fees	Upkeep, new scans and admin access, as above.

Who owns what

The code is mine. I wrote EVAR Sizing and keep the rights to it. The research team can use it for the study for as long as it runs.
The study data belongs to the research team. Everything participants record through the study is theirs. I host it and look after it for them.

What I've assumed

An estimate: every scan is 8.99 MB, the size of the one real scan I've prepared so far. I don't know the actual sizes of the scans going into the library yet, so storage and delivery will change once I've prepared them.
Every scan someone does is a fresh 8.99 MB download, and everyone has joined the study, so every case is saved. Browser caching and people who don't join only bring the numbers down.
A month is 30 days, and each person visits once a day.
A saved attempt takes about 2 KB in the database: a full attempt is 1,111 bytes of JSON, plus its columns and indexes.
A first visit to the practice downloads 0.413 MB, measured: 12 KB of HTML and 401 KB of scripts and styles.
An estimate: the API and database use about US$3.4 a month of Railway at rest, inside its US$5 minimum. Only the busiest cases outgrow it, once their study records pile up.
An estimate: each API call through Vercel uses 10 ms of CPU. At the top of every slider that's 609,000 calls and 1.7 of Hobby's 4 CPU hours a month, so the website stays free.
A resident's time is left out unless the switch is on. Switched on, it starts at $50 an hour and 15 minutes a scan.
The domain is a regular .com bought at cost. A different name or ending changes that line.
My upkeep fee is 10% of running the site, rounded to the cent, and never of the resident's time or my base fee. My base fee is $500, once, however long it runs.
Each bill is converted on its own, so twelve months at $7.00 are exactly $84.00. Storage is worked out over the whole period, because a month of it is a fraction of a cent.

Sources

All checked on October 23, 2026.